myrabolans ( myrobalans )

A vegetable tanning material obtained from the
dried astringent fruits of certain species of
Terminalia, and used extensively in the tanning of
leather. The dried fruit is rich in tannin,
averaging 30 to 32%, but the percentage varies
greatly with different grades and sources.

One of the principal advantages of myrabolan
extract, which has to a large extent replaced
sumac and plant galls in European tanneries, is
its acid-forming properties. It contains 3 to 5%
sugars, which is much more than most other tannins
contain; consequently fermentation takes place
readily in the tan liquor and satisfactory
plumping of the hides and skins is obtained in the
early stages of tanning. Myrabolan tannin also
contains a large proportion of ellagitannic acid,
and thus readily deposits bloom. The disadvantages
of the tannin are its slow penetration, and its
tendency to produce a spongy leather of poor
wearing quality. Because of these characteristics,
myrabolans is usually blended with other more
astringent tannins, e.g., wattle, quebracho, or
mangrove, which penetrate faster.

Myrabolans is a pyrogallol class of tannin, with
low viscosity, a medium pH (3.2) and salts
content, and very high acids content. The tannin
also contains chebulinic acid and a fairly high
proportion of ellagitannin.

In addition to its used in the tanning industry,
myrabolan tannin is also used as a black dye and
in the manufacture of some inks. See also:VEGETABLE TANNINS .
(175 , 298 , 306 )